Abstract. This study aims to determine the mineral contribution to PM 10 in the central Mediterranean Sea, based on 7 yr of daily PM 10 samplings made on the island of Lampedusa (35.5 • N, 12.6 • E).The chemical composition of the PM 10 samples was determined by ion chromatography for the main ions, and, on selected samples, by particle-induced X-ray emission (PIXE) for the total content of crustal markers. Aerosol optical depth measurements were carried out in parallel to the PM 10 sampling.The average PM 10 concentration at Lampedusa over the period June 2004-December 2010 is 31.5 µg m −3 , with low interannual variability. The annual means are below the EU annual standard for PM 10 , but 9.9 % of the total number of daily data exceeds the daily threshold value established by the European Commission for PM (50 µg m −3 , European Community, EC/30/1999).The Saharan dust contribution to PM 10 was derived by calculating the contribution of Al, Si, Fe, Ti, non-sea-salt (nss) Ca, nssNa, and nssK oxides in samples in which PIXE data were available. Cases in which crustal content exceeded the 75th percentile of the crustal oxide content distribution were identified as elevated dust events. Using this threshold, we obtained 175 events. Fifty-five elevated dust events (31.6 %) displayed PM 10 higher than 50 µg m −3 , with dust contributing by 33 % on average.The crustal contribution to PM 10 has an annual average value of 5.42 µg m −3 , and reaches a value as high as 67.9 µg m −3 (corresponding to 49 % of PM 10 ) during an intense Saharan dust event.The crustal content estimated from a single tracer, such as Al or Ca, is in good agreement with the one calculated as the sum of the metal oxides. Conversely, larger crustal contents are derived by applying the EU guidelines for demonstration and subtraction of exceedances in PM 10 levels due to high background of natural aerosol. The crustal aerosol amount and contribution to PM 10 showed a very small seasonal dependence; conversely, the dust columnar burden displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm up to 0.28 in June-August). We found that 71.3 % of the dust events identified from optical properties over the atmospheric column display a high dust content at the ground level. Conversely, the remaining 28.7 % of cases present a negligible or small impact on the surface aerosol composition due to the transport processes over the Mediterranean Sea, where dust frequently travels above the marine boundary layer, especially in summer.Published by Copernicus Publications on behalf of the European Geosciences Union. M. Marconi et al.: Saharan dust aerosol over the central Mediterranean SeaBased on backward trajectories, two regions, one in Algeria-Tunisia, and one in Libya, are identified as main source areas for intense dust episodes occurring mainly in autumn and winter. Data on the bulk composition of mineral aerosol arising from these two source areas are scarce; results on characteristic ratios between ele...

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Abstract. Particulate matter with aerodynamic diameters lower than 10 µm, (PM 10 ) aerosol samples were collected during summer 2013 within the framework of the Chemistry and Aerosol Mediterranean Experiment (ChArMEx) at two sites located north (Capo Granitola) and south (Lampedusa Island), respectively, of the main Mediterranean shipping route in the Straight of Sicily.The PM 10 samples were collected with 12 h time resolutions at both sites. Selected metals, main anions, cations and elemental and organic carbon were determined.The evolution of soluble V and Ni concentrations (typical markers of heavy fuel oil combustion) was related to meteorology and ship traffic intensity in the Straight of Sicily, using a high-resolution regional model for calculation of back trajectories. Elevated concentration of V and Ni at Capo Granitola and Lampedusa are found to correspond with air masses from the Straight of Sicily and coincidences between trajectories and positions of large ships; the vertical structure of the planetary boundary layer also appears to play a role, with high V values associated with strong inversions and a stable boundary layer. The V concentration was generally lower at Lampedusa than at Capo Granitola V, where it reached a peak value of 40 ng m −3 .Concentrations of rare earth elements (REEs), La and Ce in particular, were used to identify possible contributions from refineries, whose emissions are also characterized by elevated V and Ni amounts; refinery emissions are expected to display high La / Ce and La / V ratios due to the use of La in the fluid catalytic converter systems. In general, low La / Ce and La / V ratios were observed in the PM samples. The combination of the analyses based on chemical markers, air mass trajectories and ship routes allows us to unambiguously identify the large role of the ship source in the Straight of Sicily.Based on the sampled aerosols, ratios of the main aerosol species arising from ship emission with respect to V were estimated with the aim of deriving a lower limit for the total ship contribution to PM 10 . The estimated minimum ship emission contributions to PM 10 were 2.0 µg m −3 at Lampedusa and 3.0 µg m −3 at Capo Granitola, corresponding with 11 and 8.6 % of PM 10 , respectively.

Abstract. The Mediterranean basin is characterized by large concentrations of aerosols from both natural and anthropogenic sources. These aerosols change the optical properties of the atmosphere, therefore affecting tropospheric photochemistry through the photolytic rates. Two simulations of the atmospheric composition at basin-scale have been performed with the CHIMERE chemistry-transport model for the period from 1 June to 15 July 2013 covered by the ADRIMED campaign, a campaign of intense measurements in the western Mediterranean basin. One simulation takes into account the radiative effect of the aerosols on photochemistry, the other one does not. These simulations are compared to satellite and ground-based measurements, with a particular focus on the area of Lampedusa. Values of the Aerosol Optical Depth (AOD) are obtained from the MODIS instrument on the AQUA and TERRA satellites as well as from stations in the AERONET network and from the MFRSR sun photometer deployed at Lampedusa. Additional measurements from instruments deployed at Lampedusa either permanently or exceptionnally are used for other variables: MFRSR sun photometer for AOD, diode array spectrometer for actinic fluxes, LIDAR for the aerosol backscatter, sequential sampler for speciation of aerosol and Brewer spectrophotometer for the total ozone column. It is shown that CHIMERE has a significant ability to reproduce observed peaks in the AOD, which in Lampedusa are mainly due to dust outbreaks during the ADRIMED period, and that taking into account the radiative effect of the aerosols in CHIMERE improves considerably the ability of the model to reproduce the observed day-to-day variations of J(O1D) and J(NO2). While in the case of J(O1D) other variation factors such as the stratospheric ozone column are very important in representing correctly the day-to-day variations, the day-to-day variations of J(NO2) are captured almost completely by the model when the optical effects of the aerosols are taken into account. Finally, it is shown that the inclusion of the direct radiative effect of the aerosols in the CHIMERE model leads to reduced J(O1D) and J(NO2) values over all the simulation domain, which ranges from a few percents over continental Europe and the northeast Atlantic Ocean to about 20% close to and downwind from saharan dust sources. The effect on the modelled ozone concentration is twofold, with the effect of aerosols leading to reduced ozone concentrations over the Mediterranean Sea and continental Europe, close to the sources of NOx, and on the contrary to increased ozone concentrations over remote areas such the Sahara and the tropical Atlantic Ocean.

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